Practice Questions

The gel matrix of agarose acts as a molecular sieve. During electrophoresis, charged macromolecules (like DNA) move through the pores. Smaller molecules move faster and farther, while larger molecules are retarded. This sieving separates the molecules by size.

The higher density of non-reducing ends in glycogen allows more glycogen phosphorylase molecules to work simultaneously on a single molecule, dramatically increasing the rate of glucose-1-phosphate release during sudden demands for energy.

Glycogenesis is the anabolic process of converting excess glucose into glycogen for storage, primarily in the liver and muscle. Glycogenolysis is its catabolic counterpart. Gluconeogenesis is the synthesis of new glucose from non-sugar sources.

Benedict's reagent is an alkaline solution of copper(II) sulfate and sodium carbonate. In a hot alkaline environment, glucose's carbonyl group reduces Cu²⁺ to Cu⁺, forming a colored precipitate. The alkalinity is crucial for the reaction to proceed.

Epimers are a subclass of diastereomers that differ in configuration at exactly one chiral center. For example, D-glucose and D-galactose are C-4 epimers, and D-glucose and D-mannose are C-2 epimers. Anomers are epimers specifically at the hemiacetal/hemiketal carbon.

The debranching enzyme's α-1,6-glucosidase activity specifically hydrolyzes the α-1,6 bond at a branch point, releasing a free glucose molecule. This action is essential for the complete degradation of glycogen and amylopectin, as phosphorylase cannot act on or near these bonds.

Reduction of the carbonyl group of glucose (by agents like NaBH₄ or H₂ over catalyst) converts it to the sugar alcohol sorbitol (glucitol). The aldehyde (-CHO) is reduced to a primary alcohol (-CH₂OH). Oxidation would yield an acid, not an alcohol.

Lysozyme (muramidase) cleaves the β-1,4 glycosidic bond between the C1 of N-acetylmuramic acid (NAM) and the C4 of N-acetylglucosamine (NAG) in the peptidoglycan layer, causing cell wall weakening and bacterial lysis.

The notation specifies the configuration (α) of the anomeric carbon (C-1) of the first sugar, and the carbon (C-4) of the second sugar to which it is linked. This precise nomenclature is essential for describing the specific, biologically active structure of an oligo- or polysaccharide.

Cellobiose is the repeating disaccharide unit of cellulose and is formed by partial hydrolysis. It consists of two β-D-glucose molecules linked by a β-1,4 glycosidic bond. It is an isomer of maltose, which has an α-1,4 linkage.